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Earlier we looked at the evolution and variety of ctenochasmatids, focusing on the skulls. Here we take a look at Ctenochasma, Pterodaustro and a taxon that forms the best transition (Fig. 1). So far it has been called the Bamberg piece. Even so, in some traits the new taxon has also gone its own way (Fig. 1), as all sisters to transitional taxa do. We’ll call it ‘Propterodaustro’ for now, but a real generic name will be applied by its discoverers when the Bamberg specimen is officially published. For now it has only made its presence known online here and here.

Figure 1. The evolution of Pterodaustro from a sister to Ctenochasma. “Propterodaustro” , the Bamberg specimen, is a sister to the transitional taxon. As you can see, there is an increasing variety in this clade.

Similarities
Like Ctenochasma, the new taxon has a long, but not hyperelongated, rostrum, as seen in Pterodaustro. Sizewise, the new taxon is midway between the two. The neck length is transitional. The curvature and depth of the mandible and the length of the tibia relative to the metacarpus in the new taxon is midway between the two (Fig. 1). Relative to the antebrachium, the metacarpus of the more derived Pterodaustro is phylogenetically shrinking, an oddity among derived pterosaurs.

Autapomorphies
The new taxon includes a few autapomorphies found in neither Ctenochasma nor Pterodaustro. A relatively taller skull is present. The torso is relatively shorter. The scapula is no longer than the coracoid chiefly because the coracoid is relatively larger. The humerus is much shorter than the femur. The ischium does not have two posterior processes. The deltopectoral crest is ever so slightly pinched. The sternal complex is uniquely shaped. Manual 4.2 is shorter than m4.1 (fairly common among pterosaurs, but not present in Ctenochasma or Pterodaustro.) The upper teeth are longer than the lowers with small thickened lobes. Perhaps you can spot additional unique traits.

This weekend
I’ll reconstruct the new Pterodaustro with stomach stones featured in JVP and put it up against the holotype to see what overall variation, if any, is present. The specimen is obviously a Pterodaustro, so there’s no reason to reconstruct it (traditional thinking), but if there is variation, there might be something of interest to post (test, test, test).

References
The pre-Solnhofen ctenochasmatid pterosaur was covered earlier here and announced earlier here and here. Quoting from those sources (below), the discoverers appear to think they have an azhdarchid ancestor, but they are not saying that for sure.

“The 155 million year old animal is different in physique from other known species – and its remnants are extremely well preserved. Scientists speak of a major discovery. The specimen had very long arms and long legs, almost like stilts. Fish remains are found in the belly.”

“The Bamberg piece shows that these giant pterosaurs had their origin in the Jurassic period,” reports Dr. Eberhard (Dino) Frey. Such a nesting, at the base of the azhdarchidae, is not confirmed in the large pterosaur family tree. It is certain that azhdarchids had their origins in the Jurassic, but not with the Bamberg specimen. Instead those ancestors were the tiny pre-azhdarchids, like no. 42 and no. 44 reported earlier here.

This is a key taxon, long ignored.
While Darwinopterusgathered all the headlines as the “missing link” between long-tailed primitive pterosaurs and short-tailed derived pterosaurs (ahem, total rubbish), this specimen is the real long-sought transitional taxon. And it doesn’t rely on made-up fantasies like “modular evolution.” Ironically it’s been known for 140 years, but relegated to the phylogenetically discarded pile of putative “juvenile” pterosaurs simply because of its diminutive size. As it happens, phylogenetically, size meant survival of the lineage. Without shrinking, pterosaurs might have gone extinct much earlier than they ultimately did (at the end of the Cretaceous).

Figure 1. Tiny TM13104 nests as the ancestor to cycnorhamphids and ornithocheirids and germanodactylids. It’s a little scaphognathid, but distinct in its metacarpal length and tiny size, This specimen was only half the size of the smallest Scaphognathus species (see figure 2), continuing a clear size reduction trend from the twice as tall Scaphognathus holotype.

Pterodactylus? micronyx?TM 13104 (Winkler 1870, No. 34 in the Wellnhoger 1970 catalog) ~2.5 cm skull length, was considered a juvenile Pterodactylus, but it is not closely related, according to the results of the large pterosaur family tree.No. 34 was derived from a sister to the Maxberg specimen of Scaphognathus(Fig. 2)and phylogenetically preceded other tiny pterosaurs including Gmu-10157 (basal to cycnorhamphids like, BSP 1968 XV 132 and the basal ornithocheirid, Yixianopterus). Moreover, TM 13104 was also basal to the lineage of pterodactylids and germanodactylids and their kin (that encompasses all the derived short-tailed pterosaurs in this branch of the large pterosaur tree) via some of the tiniest of all pterosaurs like Ornithocephalus and No. 6 (B St 1967 I 2760 (Fig. 2).

Evolution
Overall smaller and distinct from the Maxberg specimen of Scaphognathus (Fig. 2), the skull of No. 34 had a shorter, more pointed rostrum. The skull and mandible were more gracile with smaller teeth. The naris was smaller. This is how the naris was reduced in this line of derived pterosaurs.

The entire vertebral spine was shorter and more gracile, including the tail.

The sternal complex was anteroposteriorly shorter but retained distinct lateral processes. The metacarpus was longer, subequal to the ulna. The fingers were smaller. The proximal phalanges were longer.

The ischium was broad and its rims approach both the pubis and ilium. Metatarsal 5 and digit 5 were shorter. The metatarsals were not appressed.

Just imagine how tiny the hatchlings were
One centimeter tall hatchlings of TM 13104 might not have been volant due to their high surface-to-volume ratios. Instead they may have been restricted to humid leaf litter or risk desiccation as in modern very tiny lizards (Hedges and Thomas 2001).

Figure 2. TM 13104 and kin. These tiny pterosaurs nest at the bases of several clades of much larger and later pterosaurs. The longer snouts are beginning to become apparent on these tiny pterosaurs, but not Ornithocephalus, which does not have any known descendants. These are not juveniles. None are identical to larger putative adult pterosaurs. If anyone has access to images of the rest of SMNS 81775, let me know.

The Family Tree
See the pterosaur family tree here. Note the positions of these tiny pterosaurs at the bases of major clades of larger forms. These are the real transitional taxa. Darwinopterus, you’ll note, is an interesting footnote that ultimately did not lead to any higher clades.

The Rio Pterosaur Symposium 2013 featured this talk“The basal monofenestratan Darwinopterus and its implications for the origin and basal radiation of pterodactyloid pterosaurs.” by David M. Unwin and Junchang Lü. So these two are unfortunately still promoting this falsified hypothesis.

Darren Naish in Tetrapod Zoologyhappily bought into the Darwinopterus transitional taxon fable and the wonders of “modular evolution,” which doesn’t happen anywhere else in the animal family tree. He wrote lavishly about it here. You’ll remember that he’s the one who warned his blog readers against ReptileEvolution.com.

Well…
At least in this instance, it’s not my words and images you have to watch out for, but his (I won’t try to tarnish all of Naish’s works as he did mine, because otherwise he does a damn good job in that blog, and I’m not out for blood). Sadly, in this case, Naish did not put on his scientist cap and test the Darwinopterus hypothesis. He merely accepted the report as a journalist would on the authority of its authors. Among them was Dr. David Unwin, who has been behind some of the biggest bungles in pterosaur studies including, most famously, the Sordes deep-chord wing membrane myth along with the myth of pterosaur egg burial and others.

So long as pterosaur workers continue to refuse to include tiny pterosaurs in their analyses they’ll have about as much success in resolving their family trees as they have had in the past. I’m here to suggest more inclusive alternatives that work.

With the close of the Rio Pterosaur Symposium (which I did not attend), here is the poster and abstract I created for the event. Click image to enlarge and download PDF file (1.2Mb). This poster illustrates the series of taxa leading up to pterosaurs, according to the results of the completely resolved large reptile tree, along with a gradual accumulation of pterosaurian traits, something you’ll never find in archosaurs.

Figure 1. Rio Pterosaur Symposium poster by yours truly. This lays out the lepidosaur lineage of pterosaurs going back to Paliguana based on the large reptile tree. This poster demonstrates there is no truth to the traditional hypotheses that pterosaurs essentially appeared fully formed out of nowhere within the archosaurs. Rather these are the discrete steps the lepidosaur ancestors of pterosaurs took while developing a long list of pterosaurian traits.

Lepidosaurs have been rejectedas pterosaur ancestors (Bennett 1996), but ironically this is exactly where you find them. No wonder their origins have remained mysterious to traditional paleontologists like Nesbitt (2011), Hone and Benton (2007, 2008) and others.

Of course the large reptile tree permits one to continue back in time and phylogeny to see the pterosaur ancestors all the way back to basal tetrapods, but Paliguana (Fig. 1) is a good place to start as it is the first taxon in this lineage to have upper temporal fenestrae. The present list (Fig. 1) includes terrestrial and arboreal taxa, all small and tending toward long-legged and bipedal with an increasing number of extradermal membranes.

This symposium abstract (Fig. 1) follows an earlier one (Peters 2007) that described interrelations within the Pterosauria. I thank the conveners, especially Alex Kellner and Juliana Sayao, for including it.

You can see the Rio Ptero 2013 programhere. Several of the headline topics look to expand or support reports first aired here and at www.reptileevolution.com. One appears to be arising from a very unlikely source. Other abstracts are clinging to traditional hypotheses that have been falsified. We’ll look at the most interesting of those individually in future posts.

ReferencesBennett SC 1996.The phylogenetic position of the Pterosauria within the Archosauromorpha. Zool J Linn Soc. 118:261–309.Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.Nesbitt SJ 2011.The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

With the Rio Pterosaur Symposium 2013 coming to end, I thought it appropriate to bring out one of the most important taxa in the study of pterosaurs. Ironically no one else, including its discoverer, seems to think so, except yours truly. At the two previous symposia, Dr. Peter Wellnhofer lamented, “We still don’t know where pterosaurs come from. We have no Archaeopteryx for pterosaurs.”I imagine, if he is attending the Rio symposium, he and the other traditional workers continue this lament — all of which is their own fault because they have their scientific blinders on.

So did Dr. Paul Ellenberger(1974, 1978, 1993), the first scientist to describe the small, complete, beautifully preserved impressions of a little Middle Triassic lepidosaur, Cosesaurus aviceps. Ellenberger looked at Cosesaurus more thoroughly over a longer period of time than any other worker and all he saw was a bird ancestor. Earlier here and here we looked at what details Dr. Paul Ellenberger saw in Cosesaurus, focusing on the impressions of bones. Here we’ll focus on the impressions of soft tissues. I can confirm, through personal observation of the original fossil, that these impressions are indeed present. Anyone else with a ticket to Barcelona can test these observations themselves.

Figure 1. Cranial frill of Cosesaurus compared to that of a Hoatzin. Image by Paul Ellenberger (1993).

The cranial frill (Fig. 1), like that of other lepidosaurs from Basilisk to Sphenodon, may have been retained and ossified by derived pterosaurs. Such a decoration attests to a secondary sexual trait and a possible cooling surface for this facultatively bipedal flapping sprinter. There also appears to be a thin vertical plate over the nasals, likely produced by the premaxilla ascending process. Such decorations come and go in pterosaurs and their kin.

Figure 2. Dorsal frill of Cosesaurus. Image by Paul Ellenberger (1993). That “sternal keel” is the stem-like quadrant-shaped coracoid identical to that in early pterosaurs.

The dorsal frill of Cosesaurus (Fig. 2) was inherited from Sphenodonand Huehuecuetzpalliand found the acme of its expression in Longisquama. It looks short, but continue those lines to the vertebrae and they become substantial in length.

The caudal fibers of Cosesaurus (Fig. 3) were further decorations that Ellenberger considered pre-feather shafts, but are actually just fibers, some of which near the tail tip would ultimately coalesce to become a pterosaur tail vane.

Actinofibrils also emanated from the posterior of each forelimb (Fig. 4). These would ultimately become pterosaur wings and falsify the hypothesis that pterosaurs started as gliders with proximal extradermal membranes (as in gliders). In Cosesaurus and its descendants flapping the arms while running with these fibers ultimately added thrust sufficient for flight.

Fibers and membranes emanating from the hind limbs attest to the origin of paired uropatagia in Sharovipteryx and pterosaurs. Note the presence of fibers around the knee. These attest to an insulation layer, either to trap heat or keep biting insects away from the skin.

There are very few traits that pterosaurs have that are not also found in Cosesaurus, other than the elongated manual digit 4 that framed the enlarged wing. Even so, even this trait has its genesis in Cosesaurus. Paul Ellenberger (1993) certainly made mistakes in biasing his interpretation toward birds, but he is also to be commended for his careful observations of various soft tissue impressions that are key to our understanding of these traits in pterosaurs.

Figure 4. Cosesaurus fibers from posterior forelimbs. Image by Paul Ellenberger (1993). In his quest to interpret Cosesaurus as more birdy, Ellenberger flipped the hand over so that digit 4 became his digit 2. His sternal keel is actually the quadrant-shaped coracoid stem. His broad coracoids is actually one large sternum becoming integrated into a new structure, the sternal complex.

Cosesaurus truly is the Archaeopteryx of pterosaurs, bridging the gap between lizardy forms like Huehuecuetzpalli and the flying pterosaurs. I’m not the only ones seeing these structures. Dr. Paul Ellenberger saw them a decade earlier.

A minor challenge
It would be nice if someone from the next generation of pterosaur workers would get on a plane to Barcelona and take a good look at this “Archaeopteryx of pterosaurs.” Since Science is built on testing observations, it’s just a shame that no one else in the last twenty years, other than yours truly, has confirmed Ellenberger’s key and important observations.

Of course, this would upset all sorts of paradigms and traditions if done.

Figure 6. Current interpretation of Cosesaurus with soft tissues in black. Rostral crest omitted here. This is no ordinary macrocnemid. By any measure, this is the “Archaeopteryx” of pterosaurs and needs to be recognized as such. The pes matches narrow gauge, digitigrade and occasionally bipedal Rotodactylus tracks.

Something light to refresh the palate:
A new animated film, The Croods (Dreamworks 2013) includes a number of chimaera creatures to add to the fun. It’s been out for awhile. On a rainy Saturday I saw it at the dollar show.

And they have a quad-wing bird (see above) that flies like a plesiosaur is thought to swim, with languid alternating front and back strokes.

Summary
A sweet, but not a great movie, with an odd assortment of creatures from the Croodaceaous era. Kids in the audience laughed at only a few off to the side silly/cute moments. I have to admit, a napped a little during the show, but I had a big lunch. Star Trek, on the other hand, was non-stop fantastic!

Earlier we tried to help Dr. David Hone spread the word, trying to figure out what Solnhofen specimen the Dublin (National Museum of Ireland) cast was taken from. I attempted a reconstruction, but frankly, I made some mistakes earlier, here largely rectified following a successful nesting.

Here’s the cast with and without a color overlay tracing. I still need to know the scale.

Figure 1. The Dublin cast

Figure 2. Bones color re-coded on Dublin “Pterodactylus” cast. Scale unknown. The skull shown here is inverted, mandible side up. Brown areas are filled in on the original with plaster of paris.

The radius and ulna as preserved were atypically short, as shown in the reconstruction. The cast shows that these two bones could have continued further off the matrix, so I added some length. What is the length of the torso? Hard to tell. So, there’s some guesswork here (conjecture in gray, fig. 3).

The Dublin cast (where is the original?) shares more traits with BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog), itself a tiny pre-azhdarchid rather than a relative of Pterodactylus. The feet are distinctive along with several other traits.

Figure 4. Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog) a much smaller sister to the Dublin cast pterosaur. Note the pedal morphology among other similarities.

This clade of Pterodactylus-like pterosaurs (and typically mistaken for that genus) nests at the base of flightless pterosaurs and those that ultimately became azhdarchids. So these long-necked taxa, tiny though they are, are where the elongated cervicals originated. So, if anyone wonders why azhdarchids had such long necks, they have to find their answers here. Great size came much later.

There’s not much written (that I know of) concerning these specimens. They both need more study. They seem to have been shallow water waders and competent flyers, convergent with Pterodactylus longicollum.

Today another tiny pterosaur
traditionally considered a juvenile (Wellnhofer 1970). And indeed, TM 10341does look like a baby. But not a baby Pterodactylus, but a baby Dorygnathus(Figs. 1-3).

Figure 1. I didn’t realize the teeth were so long in ?Pterodactylus spectabilis, TM10341, n1 in the Wellnhofer 1970 catalog. This is no Pterodactylus, but a tiny dorygnathid from the Late Jurassic and the ancestor to the mighty azhdarchid, Quetzalcoatlus. Click to learn more.

Figure 2. ?Pterodactylus spectabilis in situ, traced and reconstructed. The specimen is crushed and the premaxilla is twisted so that its right side is exposed, the opposite of the rest of the skull. Several of the anterior teeth make a jumble in the front.

TM 10341 had a reduced tail, a short antebrachium (radius + ulna) and a big head, but it was a tiny pterosaur. It looks like an adorable infant Dorygnathus, but we know from embryos that they actually have the proportions of adults, so TM 10341 is something new. Since pterosaurs grew isometrically from hatchlings on up, so the changes that made TM 10341 “cute” all occurred in the egg or the gene.

This is one of the surviving remnants of Dorygnathus in the Late Jurassic. Others include the similarly reduced Scaphognathus and all of its ancestors from a different line of dorygnathids along with Ctenochasma and kin from a third lineage of dorygnathids.

Figure 3. Three sister taxa to scale. At left, Dorygnathus SMNS 50164, middle Jurassic. Middle, Pterodactylus spectabilis, late Jurassic. Right, Beipiaopterus, Early Cretaceous. Size reduction and enlargement were drivers in the evolution of new morphologies.

Size reduction is what drives pterosaur evolution, bringing with it the largest changes in structure and proportion. Most of these changes are retained as subsequent taxa become larger and larger. Size reduction takes place when sexually mature half size adults lay half-size eggs over several to several thousand generations. TM 10341 was about 7.5 cm tall. Hatchlings of TM 10341 would have been only 1 cm tall.